[Will targeted therapies replace chemotherapy?]

The oncologist dream is to provide more benefit with lower toxicity. The increasing knowledge of molecular mechanism for survival and proliferation of cancer cells leads to the development of targeted therapies with impressive results for some cancers even if not associated with chemotherapy. These targeted treatments could be monoclonal antibodies or tyrosine kinase inhibitors. Inactivation of only one oncogene can lead to the regression of tumours as well as the inhibition of only one pathway with one or more inhibitors. This result is related to the oncogenic addiction of these tumours. Examples are imatinib in CML and GIST, trastuzumab in HER2 positive breast cancer, gefitinib in mutated EGFR, crizotinib in EML4-ALK positive lung cancer and, also, vemurafenib in BRAF 600E mutated metastatic melanoma. We shall specifically discuss HER2 positive breast cancer, which represent some 15-20% of breast cancers and the recent targeted and bi-targeted therapies. Trastuzumab, an anti-HER2 monoclonal antibody has changed the prognosis of the disease improving survival in the metastatic and adjuvant setting. Lapatinib, a dual tyrosine kinase inhibitor of EGFR and HER2 is approved with capecitabine in trastuzumab resistant patients and in combination with letrozole in first line. Unfortunately, 20% of patients receiving adjuvant trastuzumab relapse and metastatic patients only transienly respond to trastuzumab or lapatinib combined with chemotherapy. New HER2 targeted drugs are currently in development like pertuzumab, T-DMI or mTOR and PI3K inhibitors. New strategies combining these drugs with or without chemotherapy showed interesting results in metastatic and neoadjuvant trials. The selection of patients who will most benefit from these combinations is still a challenge. Currently, chemotherapy in association with anti-HER2 therapy remains the most effective treatment option.